The invention relates to data transmission systems in general and to impact responsive access control systems in particular.
In U.S. Pat. No. 4,197,524 to Salem, there is illustrated and described a tap actuated lock for installing on a door""s inside surface which is opened when an access combination is tapped on its outside surface. The taps are detected by an impact sensitive device which produces a sensible output in response to an impact. A typical access combination is a four-number code, for example, 4,3,2,5 which requires the tapping of a first set of four taps, a relatively long pause, the tapping of a second set of three taps, a second relatively long pause, the tapping of a third set of two taps, a third relatively long pause and finally the tapping of a fourth and last set of five taps. Such a procedure takes a relatively long time, in fact, anywhere between about 10 to 20 seconds and renders the access combination relatively insecure.
In accordance with the present invention, there is provided a data transmission system suitable for use with an impact transmissive body and comprising:
(a) a data transmitting device having a reciprocable impact impeller head for transmitting an encoded series of discrete mechanical impacts to a first surface of an impact transmissive body; and
(b) a data receiving device having an impact sensitive transducer at a second surface of the impact transmissive body substantially opposite to its first surface for picking up vibrations resultant of said series of impacts.
A data transmission system of the present invention is suitable for a wide range of both unidirectional data transmission applications, for example, transmitting readings constituting data from a sensor or a detector to data collection equipment, transmitting control signals constituting data to actuable components, for example, a solenoid, a motor, a valve and the like and bidirectional data transmission applications. Thus, envisaged applications include, but are not limited to, those in respect of which conventional wired and remote control data transmission systems may be not convenient to install or suitable to operate, for example, transmitting data respectively through and across the walls of a sealed or pressurized container or a reinforced concrete wall.
In a data transmission system of the present invention, data is preferably encoded as the time intervals between consecutive impacts thereby defining an xe2x80x9caverage impact baud ratexe2x80x9d, namely, the average number of impacts per second. For example, in the case of a solenoid driven impeller head whose minimum and maximum time intervals between consecutive impacts is 30 msec and 100 msec, respectively, and the minimum time interval increment between consecutive impacts is about 1 msec, there are 70 distinguishable intervals each of which can represent an instruction code, a data reading, and the like. With such a solenoid driven impeller head, the average impact baud rate is about 20 impacts per second, however, it is envisaged an average impact baud rate of a data transmission system of the present invention can be considerably increased.
A data transmission system of the present invention is particularly suitable for implementation in access control applications, for example, to open a mortise lock, to open a bank safe, to obtain entry into a computerized communication and control network e.g. at an automatic teller machine (ATM) and the like. In such applications, a data transmitting device effectively constitutes an electronically controlled key for typically impacting a single encoded series of impacts, namely, an access combination. In these and other applications, an encoded series of impacts includes, for example, a four interval access combination of 30, 45, 55 and 62 msec which can be transmitted in less than a quarter of a second and is one of a total of 704 (i.e. more than 25 million) combinations.